Missile threats are propagating throughout the world, with unstable nations believed to be in possession of both ballistic missiles and nuclear warheads. Attention has been directed toward countermeasures for hostile missiles. There are many aspects to the problems of engaging hostile missiles. For example, there are limitations on the knowledge of where and when a missile launch may take place, so the sensors or intelligence necessary for accurate identification and tracking may not be available or in place. If the path of the hostile missile is not known, it cannot, in general, be engaged, and may achieve its hostile intent. If sensors such as radar or infrared systems are available, they may produce useful target tracking information, but such sensors are subject to the deleterious effects of noise and various types of uncertainty, such as uncertainty as to the actual location of the sensor and its direction. These uncertainties are compounded when multiple sensors view the region in which the hostile target is found, as the differences among the sensors may result in the appearance of more hostile missiles than actually exist, or possibly fewer.
It may not be possible to locate the sensors the launch point of the hostile missile. Consequently, the missile may not be detected until it is well into its flight, as when it is in the exosphere, at which time its booster engines may be exhausted. In such a scenario, the hostile missile may have to be engaged in its terminal or ballistic phase. Engagement may be accomplished by use of an interceptor missile. Various missile tracking and interceptor missile control schemes have been proposed or used.
If countermeasures are available near the launch site of a hostile missile, engagement in the boost phase might be possible. Boost phase engagement is desirable, so as to avoid problems associated with hostile missile countermeasures. Such countermeasures may include deployment of decoy objects to tend hide the location of the reentry vehicle and to confuse the interceptor missile control system. A description of a method for targeting a reentry vehicle within a group of decoys appears in U.S. patent application Ser. No. 12/473,032 filed May 27, 2009, (now U.S. Pat. No. 8,115,148) in the name of Boardman et al. Boost phase engagement is rendered difficult by limitations on the ability of sensors to acquire the hostile missile target at or near the time of launch due to obscuring terrain features. Additionally, the boosting missile changes its mass as propellant is consumed, and the time at which the boost engine cuts off is not known in advance, so its velocity from moment to moment may be difficult to determine. Even if the track of the hostile missile is well established, additional problems with engagement involve initiation of the control system of an interceptor missile, and details of the interceptor missile controls. Boost-phase engagement of hostile missiles is described in copending U.S. patent application Ser. No. 11/958,421 filed Dec. 18, 2007, in the name of Pedersen, and in many other references.
Guidance of interceptor missiles is rendered difficult because of the transition of the hostile or target missile from boost mode to ballistic mode at some point in its trajectory. Some of the problems associated with targeting of a hostile missile are described in U.S. patent application Ser. No. 12/395,830 filed Mar. 2, 2009, (now U.S. Pat. No. 8,106,340) in the name of Diaz et al.
In the continuing race between the designers of attack missiles and the designers of countermeasures, hostile missiles are improved by becoming more sophisticated. Among such improvements is the introduction of missile maneuvers during exo-atmospheric and endo-atmospheric flight. Such maneuvers may defeat ballistic missile engagement systems which are predicated on ballistic motion of the target.
Improved missile engagement is desired.